Magnetic compositions

ABSTRACT

Compositions including carbon nanofoam are suitable for printing and magnetic ink.

BACKGROUND

This disclosure relates to magnetic compositions for printing and, morespecifically, to compositions having magnetic imaging characterrecognition capabilities.

Magnetic printing methods employ inks or toners containing magneticparticles. Various magnetic inks and toners have been used in printingdigits, characters, or artistic designs, on checks, bank notes orcurrency. The magnetic inks used for these processes may contain, forexample, magnetic particles, such as magnetite in a fluid medium, and amagnetic coating of ferric oxide, chromium dioxide, or similar materialsdispersed in a vehicle including binders and plasticizers.

In situations requiring magnetic ink character recognition (“MICR”)capabilities, the ink or toner selected should contain magneticparticles having a high level of remanence or retentivity. Retentivityis a measure of the magnetism remaining when the magnetic particle isremoved from the magnetic field, i.e., the residual magnetism. Whencharacters printed using an ink or toner having a sufficiently highretentivity are read, the magnetic particles produce a measurable signalthat can vary in proportion to the amount of material deposited on thedocument being generated.

Acicular magnetite is one type of magnetic particle that, due to itsretentivity and needle shape, has been used in magnetic inks and toners.For example, U.S. Pat. No. 3,998,160, the entire disclosure of which isincorporated by reference herein, discloses an ink that includes shapedmagnetic particles which are subjected to a magnetic aligning processwhile the ink is on a carrier in a wet state, thereby permitting theauthenticity of the printing to be verified. Unfortunately, magnetiteparticles typically need to be processed or modified to enhance magneticproperties such as retentivity. The additional processing adds cost,time, and material to the process for making the ink or tonercomposition.

It would be advantageous to provide magnetic inks and toners thatprovide a number of advantages, including, for example, advantageousprocessing times.

SUMMARY

The present disclosure provides a magnetic toner composition including acarbon nanofoam and a polymer. Also described are magnetic inkcompositions including a carbon nanofoam and a fluid carrier.

The present disclosure also provides a xerographic process that includesdepositing a toner composition on a latent electrostatic image to form atoner image, the toner composition including a carbon nanofoam;transferring the toner image to a support surface; and affixing thetransferred toner image to the substrate by heating.

Also described are magnetic ink character recognition (“MICR”) processesincluding providing a substrate having a magnetic composition includinga carbon nanofoam applied thereto to form at least one recognizablecharacter; and scanning the substrate with a reading device.

In embodiments, the present disclosure describes a magnetically readablestructure that includes a substrate having a magnetic compositionassociated with at least a portion thereof. The substrate may be paper(e.g., a check, bank note or currency) and the magnetic composition maybe configured to define a recognizable character.

DETAILED DESCRIPTION OF EMBODIMENTS

Compositions for inks and toners that are useful for magnetic inkcharacter recognition (“MICR”) processes are described herein. Thecompositions include a carbon nanofoam. Further conventional ink ortoner ingredients may also be included in the compositions.

Carbon nanofoam (also known as magnet soot) is a ferromagnetic allotropeof carbon. The carbon nanofoam particles are clusters of carbon atomslinked in graphite-like sheets that are given negative curvature by theinclusion of heptagons among the regular hexagonal pattern and strungtogether to form a web-like foam. Carbon nanofoam particles can be fromabout 1 to about 50 nanometers in diameter, in embodiments from about 5to about 10 nanometers in diameter. The magnetic properties of thecarbon nanofoam enable the carbon nanofoam of the present disclosure toreplace some or all of both the magnetic particle component and thecarbon black color pigrnent typically used in prior art ink and tonerformulations. Hence, in embodiments the compositions of the presentdisclosure are substantially free of both magnetite and carbon blackpigment. In embodiments, “substantially free” refers for example to anamount of magnetic or carbon black of from about 5% to about 0.0001% byweight of the total composition, in embodiments from about 3% to about1% by weight of the total composition. Hence, the use of the carbonnanofoam can simplify the ink or toner composition in comparison toprior art formulations since fewer components are needed.

Carbon nanofoam can be produced by high-repetition-rate laser ablationin an argon-atmosphere which results in a high collision frequencybetween carbon atoms and ions in the laser plume and argon atoms in thechamber, creating vapor temperature and density suitable for theefficient formation of 4-membered sp³ bonds typical of diamond. Pulsedlaser deposition is a process wherein a high-intensity pulsed laser beamis focused on a target in a chamber that is either evacuated or filledwith a specific gas such as argon, oxygen or nitrogen. The laser pulseablates the target material, and the ablated vapor expands into thechamber. When a substrate is placed in the path of the laser-producedplume, the vapor adheres to the surface. The repetitive plumes lay downa thin film of the ablated material which, in the case of ablated carbonhas the general appearance of soot. Processes and apparatus for pulsedlaser deposition are described, for example in U.S. Pat. No. 6,312,768,the entire disclosure of which is incorporated herein in its entirety.Ultrafast evaporation of a graphite target in atmosphere of inert gasesleads to a diffusion-limited aggregation of carbon atoms into a form ofa fractal nanometer-size granular material. The ultrafast laser ablationtechnique can provide a carbon nanofoam formation rate on the order ofabout 1 cm³/min. The bulk density of carbon nanofoam can be about 2×10⁻³g/cm⁻³ to about 10×10⁻³ g/cm⁻³, with a specific surface area comparableto that of carbon aerogels (about 300 m²/g to about 400 m²/g).

At low temperatures, the as-deposited carbon nanofoam exhibits a strongpositive electrostatic charge and non-linear current-voltagecharacteristics with strong hysteresis, indicative of its insulatingnature. After annealing, the resistivity of the carbon nanofoam measuredat low-voltage (±30 V) is about 1×10⁹ Ohm·cm to about 3×10⁹ Ohm·cm atroom temperature and about 1×10¹³ Ohm·cm at 80° K to about 10×10¹³Ohm·cm at 80° K, with virtually no hysteresis. The carbon nanofoamcontains numerous unpaired electrons, apaprently due to carbon atomswith only three bonds that are found at topological and bonding defects,so that the carbon nanofoam is attracted to magnets. Below −183° C. thecarbon nanofoam itself can be made magnetic.

The carbon nanofoam can be present in the compositions described hereinin an amount sufficient to provide an adequate MICR signal. The signalis determined by a standard calibration document as defined by theBanker's Association Standard and Specifications for MICR EncodedDocument. Generally, each country sets a minimum percent signal level,for example the minimum signal level in the USA is 50 percent of thenominal, while in Canada it is 80 percent of the nominal. To ensurelatitude in the printing process, it is generally desirable to exceedthe nominal specification, for example the target signal which is about115 to about 130 percent of the nominal to minimize the documentrejection rates. “Adequate MICR” as used herein refers to a magneticsignal from about 50 percent to about 130 percent, where 100 percentrefers, for example, to the nominal signal for readability by a checkreader, and in embodiments from about 70 percent to about 115 percent.The carbon nanofoam can advantageously have a coercivity of from about70 Oersteds (“Oe”) to about 800 Oe and in embodiments from about 250 Oeto about 500 Oe, a remanent magnetization (Br) of about 10 to about 75emu/gram and in embodiments about 23 to about 39 emu/gram, and asaturation magnetization (Bm) of about 50 to about 100 emu/gram and inembodiments about 70 to about 90 emu/gram. The carbon nanofoam can bepresent in an amount of about 0.1 to about 45 weight percent, inembodiments in an amount of about 0.1 to about 10 weight percent, and inembodiments in an amount of about 0.5 to about 5.0 weight percent of thetoner components.

Carbon nanofoam can be formulated and processed into a suitable ink ortoner using any technique. In embodiments, a magnetic ink includescarbon nanofoam and a liquid carrier. Any conventional liquid carriercan be employed. Suitable liquid carriers include, but are not limitedto, aromatic alcohols and aliphatic alcohols having from about 1 toabout 18 carbon atoms. Specific examples of suitable liquid carriersinclude one or more of the following: regular or high purity water,methanol, ethanol, iso-propyl alcohol, octane, dodecane, heptane,hexane, acetone, butyl acetate, glycol, glycerol, phenol, and the like.The liquid carrier can be present in magnetic inks in accordance withthis disclosure in amounts from about 50 percent to about 95 percent byweight of the total composition, in embodiments from about 70 percent toabout 90 percent by weight of the total composition. The magnetic inkcan be applied to a substrate upon which magnetic printing is desired,and once the liquid carrier evaporates and the ink dries, a magneticimage or text remains on the substrate.

Processes for forming toner compositions for use with reprographic orxerographic print devices are known. For example,emulsion/aggregation/coalescing processes for the preparation of drytoners are illustrated in a number of patents, such as U.S. Pat. Nos.5,290,654, 5,278,020, 5,308,734, 5,370,963, 5,344,738, 5,403,693,5,418,108, 5,364,729, and 5,346,797; and also of interest may be U.S.Pat. Nos. 5,348,832; 5,405,728; 5,366,841; 5,496,676; 5,527,658;5,585,215; 5,650,255; 5,650,256 and 5,501,935; 5,723,253; 5,744,520;5,763,133; 5,766,818; 5,747,215; 5,827,633; 5,853,944; 5,804,349;5,840,462; 5,869,215; 5,869,215; 5,863,698; 5,902,710; 5,910,387;5,916,725; 5,919,595; 5,925,488 and 5,977,210, the entire disclosures ofeach of which are incorporated herein in their entirety by reference.

In embodiments, a process of the present disclosure involves aggregatinga carbon nanofoam dispersion (including water, surfactant and,optionally a colorant) with a latex dispersion (including surfactant,water and resin), coalescing the aggregates generated, and thenisolating, washing, and drying the resulting magnetic toner.

Surfactants can be present in the carbon nanofoam and latex dispersionutilized to form the toner composition in effective amounts of, forexample, about 0.001 to about 15 weight percent, and in embodimentsabout 0.001 to about 0.1 weight percent of the toner components.Surfactants used in the toner composition can be anionic, nonionic, orcationic in nature. Examples of anionic surfactants include, forexample, sulfates including sodium dodecylsulfate (SDS), sulfonatesincluding sodium dodecylbenzene sulfonate, sodium dodecylnaphthalenesulfate, dialkyl benzenealkyl, abitic acid, and the like, and mixturesthereof. An effective concentration of the anionic surfactant generallyemployed is, for example, in an amount of about 0.01 to about 10 percentby weight, and in embodiments in an amount of about 0.1 to about 5percent by weight of monomers used to prepare the toner polymer resin.

Examples of nonionic surfactants that may be, for example, included inthe resin latex dispersion include polyvinyl alcohol, polyacrylic acid,methalose, methyl cellulose, ethyl cellulose, propyl cellulose, hydroxyethyl cellulose, carboxy methyl cellulose, polyoxyethylene cetyl ether,polyoxyethylene lauryl ether, polyoxyethylene octyl ether,polyoxyethylene octylphenyl ether, polyoxyethylene oleyl ether,polyoxyethylene sorbitan monolaurate, polyoxyethylene stearyl ether,polyoxyethylene nonylphenyl ether,dialkylphenoxypoly(ethyleneoxy)ethanol, and the like, and mixturesthereof. A suitable concentration of the nonionic surfactant is, forexample, from about 0.01 to about 10 percent by weight, in embodimentsin an amount of about 0.1 to about 5 percent by weight of monomers usedto prepare the toner polymer resin.

Examples of the cationic surfactants, which are usually positivelycharged, selected for the toners and processes of the present disclosureinclude, for example, alkylbenzyl dimethyl ammonium chloride, dialkylbenzenealkyl ammonium chloride, lauryl trimethyl ammonium chloride,alkylbenzyl methyl ammonium chloride, alkyl benzyl dimethyl ammoniumbromide, benzalkonium chloride, cetyl pyridinium bromide, C₁₂, C₁₅, C₁₇trimethyl ammonium bromides, halide salts of quatemizedpolyoxyethylalkylamines, dodecylbenzyl triethyl ammonium chloride, andthe like, and mixtures thereof. A suitable amount of surfactant can beselected, such as in an amount of about 0.1 to about 10 percent byweight of the toner components, and, in embodiments an amount of about0.2 to about 5 percent by weight of the toner components. The choice ofparticular surfactants or combinations thereof as well as the amounts ofeach to be used are within the purview of those skilled in the art.

The toner composition may also optionally contain a colorant. Colorantsinclude pigments, dyes, mixtures of pigments and dyes, mixtures ofpigments, mixtures of dyes, and the like. Suitable colorants are knownto those skilled in the art and are available from a variety ofcommercial sources. Various known colorants, such as pigments, can bepresent in the toner in an effective amount of, for example, from about1 to about 15 percent by weight of toner, and in embodiments in anamount of from about 3 to about 10 percent by weight. Suitable colorantsinclude, but are not limited to, carbon black. Generally, coloredpigments that can be selected are cyan, magenta, red, brown, orange, oryellow pigments, and mixtures thereof. Examples of magentas that may beselected include, for example, 2,9-dimethyl-substituted quinacridone andanthraquinone dye identified in the Color Index as CI 60710, CIDispersed Red 15, diazo dye identified in the Color Index as CI 26050,CI Solvent Red 19, and the like. Illustrative examples of cyans that maybe used include copper tetra(octadecyl sulfonamido) phthalocyanine,x-copper phthalocyanine pigment listed in the Color Index as CI 74160,Cl Pigment Blue, and Anthrathrene Blue, identified in the Color Index asCI 69810, Special Blue X-2137, and the like; while illustrative examplesof yellows that may be selected are diarylide yellow3,3-dichlorobenzidene acetoacetanilides, a monoazo pigment identified inthe Color Index as CI 12700, CI Solvent Yellow 16, a nitrophenyl aminesulfonamide identified in the Color Index as Foron Yellow SE/GLN, CIDispersed Yellow 33 2,5-dimethoxy-4-sulfonanilidephenylazo-4′-chloro-2,5-dimethoxy acetoacetanilide, and Permanent YellowFGL.

Illustrative examples of resins include, but are not limited to styreneacrylates, styrene butadienes, styrene methacrylates, and morespecifically, poly(styrene-butadiene), poly(methylmethacrylate-butadiene), poly(ethyl methacrylate-butadiene), poly(propylmethacrylate-butadiene), poly(butyl methacrylate-butadiene), poly(methylacrylate-butadiene), poly(ethyl acrylate-butadiene), poly(propylacrylate-butadiene), poly(butyl acrylate-butadiene),poly(styrene-isoprene), poly(methylstyrene-isoprene), poly(methylmethacrylate-isoprene), poly(ethyl methacrylate-isoprene), poly(propylmethacrylate-isoprene), poly(butyl methacrylate-isoprene), poly(methylacrylate-isoprene), poly(ethyl acrylate-isoprene), poly(propylacrylate-isoprene), poly(butyl acrylate-isoprene),poly(styrene-butylacrylate), poly(styrene-butadiene),poly(styrene-isoprene), poly(styrene-butyl methacrylate),poly(styrene-butyl acrylate-acrylic acid),poly(styrene-butadiene-acrylic acid), poly(styrene-isoprene-acrylicacid), poly(styrene-butyl methacrylate-acrylic acid), poly(butylmethacrylate-butyl acrylate), poly(butyl methacrylate-acrylic acid),poly(styrene-butyl acrylate-acrylonitrile-acrylic acid),poly(acrylonitrile-butyl acrylate-acrylic acid), and the like, andcombinations thereof. The latex polymer is generally present in thetoner compositions of the present disclosure in various effectiveamounts, such as from about 30 weight percent to about 98 weightpercent, in embodiments from about 75 weight percent to about 98 weightpercent, and in embodiments from about 85 weight percent to about 96weight percent of the toner components. The latex polymer size suitablefor the processes of the present disclosure can be, for example, fromabout 0.01 to about 1.5 microns in volume average diameter as measuredby the Brookhaven nanosize particle analyzer, and in embodiments fromabout 0.05 microns to about 1 micron in volume average diameter. Othersizes and effective amounts of latex polymer may be selected inembodiments.

In order to aid in the processing of the toner composition, counterioniccoagulant having an opposite polarity to the ionic surfactant in thelatex may optionally be used in the toner composition. The quantity ofcoagulant is present to, for example, prevent/minimize the appearance offines in the final slurry. Fines refer to small sized particles of lessthan about 1 micron in average volume diameter, which can adverselyaffect toner yield. Counterionic coagulants may be organic or inorganicentities. For example, in embodiments of the present disclosure, theionic surfactant of the resin latex dispersion can be an anionicsurfactant, and the counterionic coagulant can be a polymetal halide ora polymetal sulfo silicate (PASS). Exemplary coagulants that can beincluded in the toner include polymetal halides, polymetalsulfosilicates, monovalent, divalent or multivalent salts optionally incombination with cationic surfactants, and the like. Inorganic cationiccoagulants include, for example, polyaluminum chloride (PAC),polyaluminum sulfo silicate (PASS), aluminum sulfate, zinc sulfate, ormagnesium sulfate. When present, the coagulant is used in an amount ofabout 0.05 to about 10 weight percent, in embodiments in an amount ofabout 0.075 to about 2 weight percent of the total toner composition.

Further optional additives surface additives, color enhancers, and thelike. Surface additives include, for example, metal salts, metal saltsof fatty acids, colloidal silicas, metal oxides, mixtures thereof andthe like, which additives may be present in an amount of about 0.05 toabout 5 percent and in embodiments in an amount of about 0.1 to about 2percent by weight of the total toner composition. See, U.S. Pat. Nos.3,590,000, 3,720,617, 3,655,374 and 3,983,045, the entire disclosures ofeach of which are incorporated herein by reference.

The dry toner compositions illustrated herein can be prepared by anumber of known methods, including mechanical blending and melt blendingthe toner resin particles, carbon nanofoam, and surfactants followed bymechanical attrition. Other methods include those well known in the artsuch as spray drying, mechanical dispersion, melt dispersion, dispersionpolymerization, and suspension polymerization. More specifically, thetoner compositions may be prepared by the simple mixing of carbonnanofoam, polymeric resin, and additive particles while heating,followed by cooling. After cooling, the composition may be subjected tomicronization to obtain toner size particles of, for example, an averagediameter of about 5 microns to about 25 microns, and subsequentlyclassifying these particles for the primary purpose of removing fines,for example particles with a diameter of about 4 microns or less, andvery large coarse particles, for example, with a diameter of greaterthan about 30 microns. Also, the aforementioned toners can be preparedin a similar manner with an extrusion device wherein the product exitingfrom such a device is severed into pieces followed by micronization andclassification.

Developer compositions can be prepared by mixing the toners inaccordance with the present disclosure with known carrier particles,including coated carriers, such as steel, ferrites, and the like, asdisclosed in U.S. Pat. Nos. 4,937,166 and 4,935,326, the entiredisclosures of each of which are incorporated herein by reference. Inembodiments, the developer compositions may contain, for example fromabout 2 percent toner concentration to about 8 percent tonerconcentration.

In embodiments, a toner for MICR according to the present disclosureincludes at least a binder resin, carbon nanofoam and a wax as maincomponents, and optionally contains a coloring agent, a releasing agentother than the wax, a charge controlling agent and other additives. Afluidizing agent may also be allowed to attach to the surface of tonerparticles.

Specific examples of the binder resin of the toner which may be utilizedinclude homopolymers and copolymers of styrene and substituted styrenesuch as polystyrene, poly-p-chlorostyrene, polyvinyltoluene,styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, andthe like; copolymers of styrene and acrylic acid ester such asstyrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer,styrene-n-butyl acrylate copolymer, and the like; copolymers of styreneand methacrylic acid ester such as styrene-methyl methacrylatecopolymer, styrene-ethyl methacrylate copolymer, styrene-n-butylmethacrylate copolymer, and the like; styrene-acrylic acidester-methacrylic acid ester terpolymer; styrene copolymers composed ofstyrene and other vinyl monomers such as styrene-acrylonitrilecopolymer, styrene-vinyl methyl ether copolymer, styrene-butadienecopolymer, styrene-vinyl methyl ketone copolymer,styrene-acrylonitrile-indene copolymer, styrene-maleic acid estercopolymer, and the like; polymethyl methacrylate, polybutylmethacrylate, polyacrylic acid ester resin, polyester resin, polyvinylacetate, polyamide resin, epoxy resin, polyvinyl butyral resin,polyacrylic acid-phenol resin, phenol resin, aliphatic or alicyclichydrocarbon resin, petroleum resin, chlorinated paraffin, polyvinylchloride, polyvinylidene chloride, and the like, which can be used aloneor as a mixture of two or more of them. In embodiments, the binder resinincludes poly(styrene butyl acrylate beta CEA) and poly(styrene butylacrylate divinyl benzene beta CEA). The content of the resin binder inthe toner can be from about 30 to about 98% by weight, and inembodiments about 70 to 98% by weight.

The wax is added in order to ensure excellent releasing property betweena heating roll for fixation and the toner or to ensure excellentresistance against sliding friction with the magnetic head. In such acase, it is advantageous to add a wax having a DSC melting point in anamount of about 60° C. to about 110° C. and in embodiments about 85° toabout 100° C. Illustrative examples of suitable waxes includehydrocarbon waxes, such as, polyolefin wax (such as polyethylene andpolypropylene having a low molecular weight), paraffin wax,Fischer-Tropsch wax, carnauba wax, candelilla wax, rice wax, and thelike. These waxes can be used alone or in various combinations. Thecontent of the wax in the toner can be from about 2 to about 15% byweight, and in embodiments about 4 to about 10% by weight.

The toner for MICR may also contain a charge controlling agent. Chargecontrolling agents are classified into a charge controlling materialwhich affords positive charge to the toner and a charge controllingmaterial which affords negative charge to the toner. Specific examplesof the positive charge controlling material include nigrosine andnigrosine modified with a metal salt of fatty acid, quaternary ammoniumsalts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate,tetrabutylammonium tetrafluoroborate, and the like, di-organo-tin oxidessuch as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide, andthe like, di-organo-tin borates such as dibutyltin borate, dioctyltinborate, dicyclohexyltin borate, and the like Charge controlling agentscan be used alone or in combinations of two or more thereof. Specificexamples of the negative charge controlling material includeorganometallic compounds and chelate compounds such as acetylacetonemetal chelate, monoazo metallic chelate, metallic chelate or salt ofnaphthoic acid or salicylic acid, and combinations thereof. Chargecontrolling agents can be present in amounts from about 0.05 to about10% by weight and in embodiments amounts from about 0.1 to about 5% byweight.

Suitable coloring agents may optionally be utilized. Colorants includepigments, dyes, mixtures of pigments and dyes, mixtures of pigments,mixtures of dyes, and the like. Suitable colorants are known to thoseskilled in the art and are available from a variety of commercialsources. Various known colorants, such as pigments, can be present inthe toner in an effective amount of, for example, from about 1 to about15 percent by weight of toner, and in embodiments in an amount of fromabout 3 to about 10 percent by weight. Suitable colorants include, butare not limited to, carbon black. Generally, colored pigments that canbe selected are cyan, magenta, red, brown, orange, or yellow pigments,and mixtures thereof. Examples of magentas that may be selected include,for example, 2,9-dimethyl-substituted quinacridone and anthraquinone dyeidentified in the Color Index as CI 60710, CI Dispersed Red 15, diazodye identified in the Color Index as CI 26050, CI Solvent Red 19, andthe like. Illustrative examples of cyans that may be used include coppertetra(octadecyl sulfonamido) phthalocyanine, x-copper phthalocyaninepigment listed in the Color Index as CI 74160, Cl Pigment Blue, andAnthrathrene Blue, identified in the Color Index as CI 69810, SpecialBlue X-2137, and the like; while illustrative examples of yellows thatmay be selected are diarylide yellow 3,3-dichlorobenzideneacetoacetanilides, a monoazo pigment identified in the Color Index as CI12700, CI Solvent Yellow 16, a nitrophenyl amine sulfonamide identifiedin the Color Index as Foron Yellow SE/GLN, CI Dispersed Yellow 332,5-dimethoxy-4-sulfonanilide phenylazo-4′-chloro-2,5-dimethoxyacetoacetanilide, and Permanent Yellow FGL.

Further, higher fatty acid (e.g., stearates, oleates, behenates and thelike), olefin-maleic acid anhydride copolymer, and the like may be addedto the toner in amounts from about 0.5 to about 50% by weight, and inembodiments from about 1 to about 30% by weight. Also, it may beadvantageous to attach a fluidizing agent to the surface of tonerparticles. Suitable fluidizing agents include silica (e.g., hydrophobicsilica) and titanium dioxide. Fluidizing agents may be present inamounts from about 0.1 to about 5% by weight, and in embodiments fromabout 0.5 to about 2% by weight.

The toner for MICR can be produced by any known method includingblending the above mentioned components, melting with kneading themixture and pulverizing the resultant mass. Moreover, it may be producedby a polymerization method which includes blending monomers for thebinder with other ingredients and polymerizing the mixture.

In embodiments of the present disclosure, an imaging process iscontemplated. The imaging process includes the generation of an image inan electronic printing magnetic image character recognition apparatusand thereafter developing the image with a toner composition of thepresent disclosure. The formation and development of images on thesurface of photoconductive materials by electrostatic means is wellknown. The basic xerographic process involves placing a uniformelectrostatic charge on a photoconductive insulating layer, exposing thelayer to a light and shadow image to dissipate the charge on the areasof the layer exposed to the light and developing the resulting latentelectrostatic image by depositing on the image a finely-dividedelectroscopic material referred to in the art as “toner”. The toner willnormally be attracted to those areas of the layer which retain a charge,thereby forming a toner image corresponding to the latent electrostaticimage. This powder image may then be transferred to a support surfacesuch as paper. The transferred image may subsequently be permanentlyaffixed to the support surface as by heat. Instead of latent imageformation by uniformly charging the photoconductive layer and thenexposing the layer to a light and shadow image, one may form the latentimage by directly charging the layer in image configuration. Thereafter,the powder image may be fixed to the photoconductive layer ifelimination of the powder image transfer step is desired. Other suitablefixing means such as solvent or overcoating treatment may be substitutedfor the foregoing heat fixing step.

The present disclosure also provides a magnetic ink concentratecontaining carbon nanofoam particles in water or alcohol in the presenceof a dispersant, and processes for the preparation of such inks. Thesemagnetic inks are suitable, for example, for use in connection withinkjet printers.

Magnetic inks may be in the form of dispersions of carbon nanofoamparticles in water or alcohol in the presence of a dispersant, whereinthe dispersant consists of at least one polyelectrolyte.Polyelectrolytes which are suitable for the magnetic ink concentrateshave a molecular weight of from about 1,000 to about 25,000, in someembodiments from about 3,500 to about 10,000. Specific examples ofsuitable polyelectrolytes include polyacrylic acid, acrylicacid/acrylamide copolymers and polyvinylphosphonic acid, and the alkalimetal salts of these compounds. Conventional carriers, such as water oralcohols, can be used as carriers for the present magnetic inkconcentrates. Examples of alcohols are ethylene glycol, diethyleneglycol, glycerol, and mixtures of these alcohols with water. The amountof these substances is based on the specific surface area of the carbonnanofoam particles and is not less than about 0.7 mg per m² of surfacearea, in embodiments from about 1.5 to about 5 mg/m² can be particularlyadvantageous.

In addition to these components, the magnetic ink concentrates of thepresent disclosure may also contain additives for regulating the flowbehavior of the concentrate, for example alkyl phenolates. It is alsopossible to add high boilers, such as diethylene glycol, ethyleneglycol, glycerol and polyethylene glycol in minor amounts forestablishing advantageous flow and drying properties. By addingcolorants or dyes, it is also possible to vary the depth of the inkconcentrates, provided that saturation magnetization is not adverselyaffected.

The magnetic ink concentrates of the present disclosure can be preparedin a conventional manner. In embodiments a mixture of water or alcoholand the polyelectrolyte and/or its alkali metal salt in the form of asolution having a strength of about 10% to about 90% by weight isstirred with the carbon nanofoam, and the suspension is then dispersedfor from about 30 minutes to about 2 hours under the action of highshear forces. The temperature may increase to about 70° C. during thisprocedure. The components may be added in any order. Centrifuging isthen carried out for a time from about 10 minutes to about 2 hours atfrom about 200 G to about 2,000 G, and any sedimented particles areseparated off. The resulting product corresponds to the magnetic inkconcentrates.

The magnetic ink concentrates of the present disclosure are very usefulas a magnetic ink for writing apparatuses, for example inkjet printers.The resulting text image is mar-resistant, crisp, not blurred. Themagnetic ink concentrates can also be used for information storage bymeans of a magnetic bar code since the high magnetic susceptibilitymakes it particularly suitable for this purpose.

Magnetically readable structures are also contemplated by thisdisclosure. The magnetically readable structure includes a substratehaving a magnetic composition disposed thereon. The magnetic compositioncontains carbon nanofoam and can be, for example, any of thecompositions described above. The substrate may be made of any materialand, in embodiments is paper, such as a check, a bank note or currency.The substrate may also be made of plastic, such as a swipe card, creditcard or the like. In embodiments, the substrate is not limited to sheetsor cards but rather can have any shape. For example, the substrate maybe factory or store inventory that is imprinted with a carbonnanofoam-containing magnetic composition in accordance with the presentdisclosure. In such instances, the magnetic reading or characterrecognition can be achieved by passing the object so labeled over amagnetic scanner or by using a hand-held magnetic scanner.

The following Examples illustrate embodiments of the present disclosure.These Examples are intended to be illustrative only and are not intendedto limit the scope of the present disclosure. Also, parts andpercentages are by weight unless otherwise indicated.

EXAMPLES

Preparation of Starting Materials

A non-crosslinked latex comprised of 40 weight percent of submicron, 0.5micron diameter resin particles of styrene/butylacrylate/β-CEA suspendedin an aqueous phase containing anionic surfactant (“Latex A”), across-linked latex comprised of 40 percent crosslinked resin, (resinratio is 65:35:3 pph:1 pph of styrene:butyl acrylate: β-CEA:DVB) 58.5percent water and 1.5 percent anionic surfactant (“Latex B”), a waxdispersion containing a low molecular weight wax and an anionicsurfactant/dispersant wherein the wax slurry has a solid loading of 30percent (weight percent throughout), and a pigment dispersion containing19 percent carbon black, 2 percent of an anionic surfactant, and 79percent water are prepared as described in U.S. Pat. No. 6,767,684, theentire disclosure of which is incorporated herein by this reference.

Example I

A magnetic toner composition is prepared as follows:

110 Grams of carbon nanofoam is added to 600 grams of water containing1.3 grams of 20 percent aqueous anionic surfactant (NEOGEN RK™). Theresultant mixture is then polytroned or homogenized for a period of 3minutes at speeds of 5,000 rpm to provide a carbon nanofoam dispersion.To the resulting carbon nanofoam dispersion is added 90 grams of adispersion of the above submicron polyethylene P850 wax particles (30percent solids) followed by the addition of 285 grams of the aboveprepared anionic Latex A comprising submicron latex particles (40percent solids) of styrene/butylacrylate/beta CEA, and 37.5 grams of thecrosslinked Latex B of styrene/butylacrylate/divinyl benzene beta CEA(40 percent solids) and then polytroned at speed of 5,000 rpm for aperiod of 5 minutes. 300 Grams of water is then added to reduce theviscosity of the resulting blend to which then is added an aqueouspolyaluminum chloride (PAC) coagulant solution comprising 2.25 grams of10 percent solids placed in 23 grams of 0.3 M nitric acid.

The resulting blend is then heated to a temperature of 50° C. whilestirring for a period of 30 minutes to obtain a particles size fromabout 5.0 to about 5.5. To this is added a cationic surfactant of 1.6grams of alkylbenzyl dimethyl ammonium chloride SANIZOL B™ (50 percentsolids), dissolved in 15 grams of water. The mixture is then stirred fora period of 90 minutes to produce toner size aggregates from about 5.5to about 6.0 microns. 120 Grams of the above noncrosslinked latex arethen added to the aggregate mixture and stirred at 50° C. for anadditional 30 minutes to provide a particle size from about 6.0 to about7.0 microns. The aggregate mixture is then stabilized from furthergrowth by changing the pH of the mixture from about 2.6 to about 7.3with an aqueous solution of 4 percent sodium hydroxide. The resultingmixture is then heated to 93° C. during which the pH is from about 7.2to about 7.4 with the addition of aqueous 4 percent sodium hydroxidesolution. After 1 hour at 93° C., the pH is reduced in stages of 6.5followed by 5.7 after an additional 30 minutes to an aqueous 1.25percent of nitric acid solution. After a period of 6 hours at 93° C.,the particle size measured is from about 6.0 to about 7.5 microns. Theresultant mixture is cooled and the toner obtained is washed 4 timeswith water and dried on a freeze dryer. The resulting toner, whendeveloped by an electrographic process on a document, provides anadequate MICR signal for the encoded document while also beingsubstantially free of carbon black pigment and magnetite.

Example II

A magnetic toner composition is prepared as follows:

110 Grams of carbon nanofoam is added to 600 grams of water containing1.3 grams of 20 percent aqueous anionic surfactant (NEOGEN RK™) to which82.5 grams of the above 19 percent carbon black pigment dispersion isadded. The resultant mixture is then polytroned or homogenized for aperiod of 3 minutes at speeds of 5,000 rpm to provide a carbonnanofoam/pigment dispersion. To the resulting carbon nanofoam/pigmentdispersion is added 90 grams of a dispersion of the above submicronpolyethylene P850 wax particles (30 percent solids) followed by theaddition of 285 grams of the above prepared anionic Latex A comprisingsubmicron latex particles (40 percent solids) ofstyrene/butylacrylate/beta CEA, and 37.5 grams of the crosslinked LatexB of styrene/butylacrylate/divinyl benzene beta CEA (40 percent solids)and then polytroned at speed of 5,000 rpm for a period of 5 minutes. 300Grams of water is then added to reduce the viscosity of the resultingblend to which then is added an aqueous PAC coagulant solutioncomprising 2.25 grams of 10 percent solids placed in 23 grams of 0.3 Mnitric acid.

The resulting blend is then heated to a temperature of 50° C. whilestirring for a period of 30 minutes to obtain a particles size fromabout 5.0 to about 5.5. To this is added a cationic surfactant of 1.6grams of alkylbenzyl dimethyl ammonium chloride SANIZOL B™ (50 percentsolids), dissolved in 15 grams of water. The mixture is then stirred fora period of 90 minutes to produce toner size aggregates from about 5.5to about 6.0 microns. 120 Grams of the above noncrosslinked latex arethen added to the aggregate mixture and stirred at 50° C. for anadditional 30 minutes to provide a particle size from about 6.0 to about7.0 microns. The aggregate mixture is then stabilized from furthergrowth by changing the pH of the mixture from about 2.6 to about 7.3with an aqueous solution of 4 percent sodium hydroxide. The resultingmixture is then heated to 93° C. during which the pH is from about 7.2to about 7.4 with the addition of aqueous 4 percent sodium hydroxidesolution. After 1 hour at 93° C., the pH is reduced in stages of 6.5followed by 5.7 after an additional 30 minutes to an aqueous 1.25percent of nitric acid solution. After a period of 6 hours at 93° C.,the particle size measured is from about 6.0 to about 7.5 microns. Theresultant mixture is cooled and the toner obtained is washed 4 timeswith water and dried on a freeze dryer. The resulting toner, whendeveloped by an electrographic process on a document, provides anadequate MICR signal for the encoded document.

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also thatvarious presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art which are also intended to beencompassed by the following claims.

What is claimed is:
 1. A magnetic toner composition comprising a carbonnanofoam and a polymer, wherein the toner composition is substantiallyfree of a magnetite.
 2. The magnetic toner composition of claim 1,wherein the carbon nanofoam is present in an amount from about 0.1 toabout 45 percent by weight of the total toner composition.
 3. Themagnetic toner composition of claim 1, wherein the carbon nanofbam ispresent in an amount from about 0.1 to about 10 percent by weight of thetotal toner composition.
 4. The magnetic toner composition of claim 1,wherein the polymer is selected from the group consisting ofpoly(styrene-alkyl acrylate), poly(styrene-1,3diene), poly(styrene-alkylmethacrylate), poly(styrene-alkyl acrylate-acrylic acid),poly(styrene-1,3-diene-acrylic acid), poly(styrene-alkylmethacrylate-acrylic acid), poly(alkyl methacrylate-alkyl acrylate),poly(alkyl methacrylate-aryl acrylate), poly(aryl methacrylate-alkylacrylate), poly(alkyl methacrylate-acrylic acid), poly(styrene-alkylacrylate-acrylonitrile-acrylic acid),poly(styrene-1,3-diene-acrylonitrile-acrylic acid), poly(alkylacrylate-acrylonitrile-acrylic acid), poly(styrene-butadiene),poly(methylstyrene-butadiene), poly(methyl methacrylate-butadiene),poly(ethyl methacrylate-butadiene), poly(propyl methacrylate-butadiene),poly(butyl methacrylate-butadiene), poly(methyl acrylate-butadiene),poly(ethyl acrylate-butadiene), poly(propyl acrylate-butadiene),poly(butyl acrylate-butadiene), poly(styrene-isoprene),poly(methylstyrene-isoprene), poly(methyl methacrylate-isoprene),poly(ethyl methacrylate-isoprene), poly(propyl methacrylate-isoprene),poly(butyl methacrylate-isoprene), poly(methyl acrylate-isoprene),poly(ethyl acrylate-isoprene), poly(propyl acrylate-isoprene),poly(butyl acrylate-isoprene); poly(styrene-propyl acrylate),poly(styrene-butyl acrylate), poly(styrene-butadiene-acrylic acid),poly(styrene-butadiene-methacrylic acid),poly(styrene-butadiene-acrylonitrile-acrylic acid), poly(styrene-butylacrylate-acrylic acid), poly(styrene-butyl acrylate-methacrylic acid),poly(styrene-butyl acrylate-acrylononitrile), poly(styrene-butylacrylate-acrylononitrile-acrylic acid) and optionally mixtures thereof.5. The magnetic toner composition of claim 1, wherein the polymer ispresent in an amount from about 30 to about 98 percent by weight of thetotal toner composition.
 6. The magnetic toner composition of claim 1,further comprising one or more components selected from the groupconsisting of surfactants, coagulants, colorants, waxes and optionallymixtures thereof.
 7. A xerographic system comprising a chargingcomponent, an imaging component, a development component, a transfercomponent and a fixing component, wherein the development componentcomprises a toner in accordance with claim
 1. 8. The magnetic tonercomposition of claim wherein the carbon nanofoam has a coercivity offrom about 70 Oersteds to about 800 Oersteds.
 9. The magnetite tonercomposition of claim 1, wherein the magnetic toner composition issubstantially free of carbon black.